FML, I've had to try to color matching by eye before between different screens by the same manufacturer.
For whatever reason I wasn't provided with any calibration tools. I had some vague software tools to try and get them to align.
I spent like 8 hours trying to match these for the corporate brand colors, while still looking decent for everything else.
Shit is near impossible. If the manufacturer couldn't do it, how am I supposed to?! And with awful interfaces and no concrete way of measuring.
Like, I was taking pictures of the screens, then trying to figure out offsets and how they might relate to gamma triangles.
Client was appreciative of my (and fellow techs) efforts, but ultimately wasn't happy, and it looked shit.
That was awkward as fuck.